This invention relates to ball separators for use in ball bearings; and more particularly to molded plastic ball separators having means to minimize friction between the separator and the balls. The term "ball separator" refers to a component of a ball bearing assembly which is also commonly known by the names "ball retainer" and "bearing cage".
The use of ball bearing assemblies including ball retainers fabricated from molded plastic and having spherical or cylindrical pockets is well known. In such bearing assemblies, if the clearance between the balls and the ball pockets is too large, the bearing is quite noisy. Conversely, if the clearance is too small, it is difficult to retain lubricant between the surfaces of the balls and the ball pockets resulting in excessive heat buildup due to friction. A problem related to excessive heating of the bearing and separator, is that with a molded plastic type of separator the separator extends much more rapidly with heat than does the steel races of the assembly. The inherent result is that the radial expansion of the separator ring is significantly greater than the radial expansion of the races; and with small clearance between the separator pockets and the balls this unequal expansion may create binding and more friction, thereby aggravating the overheating problem.
A particular problem with respect to bearing retainers having spherical pockets, is that the relatively sharp edges of the spherical pockets act to wipe lubricant from the balls, thereby reducing the effectiveness of the lubricant and further aggravating the overheating problem.
While these problems may be alleviated by increasing the ball to ball pocket clearance, this produces a relatively loose separator resulting in separator vibration and resultant noise. The resultant separator noise may raise the overall bearing noise to an unacceptable level, particularly at high speed.
A principal object of this invention therefore is to provide an improved ball separator which overcomes the problems and disadvantages of prior art separators discussed above.
Another of this invention is to provide an improved molded plastic bearing separator having pocket surfaces which enable minimum clearance between the ball pocket surface and the balls and at the same time to reduce the surface contact area.
A further object of this invention is to provide an improved ball separator having ball pocket surfaces providing tangential ball contact areas, and defining lubricant retaining recesses between the ball contact areas.
A further object of this invention is to provide an improved molded plastic ball separator wherein the ball pockets have means for retaining lubricant for deposit to the ball surfaces and wherein the pocket configuration minimizes the effect of wiping lubricant from the ball surfaces.
Another object of this invention is to provide an improved ball bearing retainer which provides reduced starting torque for the bearing assembly.
Still another object of this invention is to provide an improved molded plastic ball separator for a ball bearing assembly which reduces ball contact areas, reduces friction, and reduces noise, and which is economic to fabricate.
These objects are accomplished in a ball separator for use in a ball bearing which includes confronting first and second races and a plurality of spherical balls coacting with said races. The ball separator includes an annular base, and includes a plurality of annularly spaced fingers projecting from the annular base to define individual annularly spaced ball pockets. The ball separator has opposite side walls which are configured to be received between the outer and inner races of the ball bearing with the side walls confronting respective races. Each of the ball pockets is formed to partially enclose a respective ball, and has a wall surface configured to provide clearance between the pocket and the ball. Each ball pocket wall surface comprises a plurality of surface segments providing ball contact areas; and the surface segments define lubricant retaining recesses between and adjacent to the ball contact areas.
More particularly the surface segments may be contiguous to each other, and may be planar, cylindrical, or spherical providing tangential contact areas.
The novel features and the advantages of the invention as well as additional objects thereof will be understood more fully from the following description when in connection with the accompanying drawings.